Histrelin is an LHRH agonist with which there is considerable human experience, although not when delivered by implant. It is recently been approved by the US FDA for inhibition of early puberty in children. Potent LHRH agonists when administered frequently, or even more effectively, continuously, cause desensitization of the pituitary and markedly reduced circulating levels of LH. This, in turn, suppresses testosterone synthesis. Based on experience with other analogues given by injection, depression to essentially castrate levels can be attained. This is a desired end in treatment of symptoms associated with prostate cancer. A subdermal implant would constitute a convenient way of continuously dosing with an LHRH agonist. Such an implant has been developed and shown in vitro and in animal studies to deliver an essentially constant dose of a period of six months or longer. The rate controlling membrane is a hydrogel. Specific goals of the study are: determine whether these histrelin delivering implants can be used in humans; ascertain the dose of histrelin necessary to suppress gonadotropin and testosterone secretions; and determine the blood levels of histrelin during effective treatment.